Dispenser units arranged to dispense countermeasures from aircrafts are well known. Both fighter and transport aircrafts, as well as civil aircrafts are exposed for threats from self-guided missiles equipped with radar, IR or laser sensors, which can be fired either from other aircrafts or from the ground. In order to protect the threatened aircrafts from an attack of such missiles they are provided with various types of dispenser units which dispense countermeasure means. Such countermeasure means may comprise aluminized foil or fibers, pyrophoric IR materials, flares and also laser-reflecting fibers or foils, which confuse and divert missiles aimed at the aircraft.
Document EP-A1-0511946 discloses a dispenser for feeding out packages containing chaff, which dispenser may be arranged on an aircraft. The dispenser is provided with air guiding means in order to create a pressure difference at a feeding out opening pulling out the packages in the air stream behind the dispenser. The air guiding means are air scoops provided with an air inlet in connection to the side of the dispenser and an air outlet in connection to the feeding out opening.
Commonly, the dispenser is applied on the under side of an aircraft, preferably an airplane, and has an elongated body shape with its longitudinal direction coinciding with the flight direction of the air craft. The elongated body is exposed to air streaming having a speed corresponding to the flight speed of the aircraft. The feeding out opening of a magazine for packages provided with chaffs terminates in the rear section of the dispenser. During a flight a wake is formed behind the feeding out opening. Immediately behind the dispenser, the wake has a sectional area of the same order of magnitude as the sectional area of the dispenser. The formation of this wake inter alia influences on the separation time of the packages with chaffs, which is the time required for the package located closest to the feeding out opening to separate from the rest of the packages in the magazine and to leave the feeding out opening.
However, the packages containing chaff are only fed out at moments when the aircraft is under attack or at moments when the aircraft is under a potential threat. Therefore, the air guiding means in form of air scoops have no function when the dispenser is inactivated and the packages containing chaff are not fed out from the dispenser. During a mission the feeding out packages containing chaff takes place under a relatively short period of time in relation to the overall flight time of the mission. As a result, the need of the air scoops is only limited to a relatively short period of time in relation to the overall flight time of the mission.
The air scoops have a negative influence on the air drag and therefore the fuel consumption of the aircraft will increase. As a result, the operation range of the aircraft will decrease when the fuel consumption increases. Also, the air scoops could create noise which may be detected by an enemy in order to detect the position of the aircraft.
The objective problem to be solved by the present invention is therefore to reduce the air drag of the air scoops when the dispenser is not activated.
Another objective problem to be solved by the present invention is to reduce noise created by the air scoops when the dispenser is not activated.